"The great tides at the close of the Middle Ages, with their accompanying snow and ice, furious winds, and inundating floods, are more than five centuries behind us. The era of weakest tidal movements, with a climate as benign as that of the early Middle Ages, is about four centuries ahead. We have therefore begun to move strongly into a period of warmer, milder weather. There will be fluctuations, as earth and sun and moon move through space and the tidal power waxes and wanes. But the long trend is toward a warmer earth; the pendulum is swinging."
RACHEL CARSON ON 'CLIMATE CHANGE'
"...day by day and season by season, the ocean dominates the world’s climate. Can it also be an agent in bringing about the long period swings of climatic change that we know have occurred throughout the long history of the earth the alternating periods of heat and cold, of drought and flood?
There is a fascinating theory that it can. This theory links events in the deep, hidden places of the ocean with the cyclic changes of climate and their effects on human history. It was developed by the distinguished Swedish oceanographer, Otto Pettersson, whose almost century-long life closed in 1941- In many papers; Pettersson presented the different facets of his theory as he pieced it together, bit by bit. Many of his fellow scientists were impressed, others doubted. In those days few men could conceive of the dynamics of water movements in the deep sea. Now the theory is being re-examined in the light of modern oceanography and meteorology, and only recently C. E. P. Brooks said: ‘It seems that there is good support for Pettersson’s theory as well as for that of solar activity, and that the actual variations of climate since about 3000 B.C. may have been to a large extent the result of these two agents.’
He had found that the submarine waves varied in height and power as the tide producing power of the moon and sun varied. From astronomical calculations he learned that the tides must have been at their greatest strength during the closing centuries of the Middle Ages- those centuries when the Baltic herring fishery was flourishing. Then sun, moon, and earth came into such a position at the time of the winter solstice that they exerted the greatest possible attracting force upon the sea. Only about every eighteen centuries do the heavenly bodies assume this particular relation. But in that period of the Middle Ages, the great underwater waves pressed with unusual force into the narrow passages to the Baltic, and with the ‘water mountains’ went the herring shoals. Later, when the tides became weaker, the herring remained outside the Baltic, in the North Sea.
Then Pettersson realized another fact of extreme significance - that those centuries of great tides had been a period of ‘startling and unusual occurrences’ in the world of nature. Polar ice blocked much of the North Atlantic. The coasts of the North Sea and the Baltic were laid waste by violent storm floods. The winters were of ‘unexampled severity’ and in consequence of the climatic rigours political and economic catastrophes occurred all over the populated regions of the earth. Could there be a connection between these events and those moving mountains of unseen water? Could the deep rides affect the fives of men as well as of herring?
From this germ of an idea, Pettersson’s fertile mind evolved a theory of climatic variation, which he set forth in 1912 in an extraordinarily interesting document called "Climatic Variations in Historic and Prehistoric Time." Marshaling scientific, historic, and literary evidence, he showed that there are alternating periods of mild and severe climates which correspond to the long-period cycles of the oceanic tides. The world’s most recent period of maximum tides, and most rigorous climate, occurred about 1433, its effect being felt, however, for several centuries before and after that year. The minimum tidal effect prevailed about A. D. 550, and it will occur again about the year 2400.
Marshaling scientific, historic, and
literary evidence, he showed that there are alternating periods of mild and severe climates
which correspond to the long-period cycles of the oceanic tides. The world’s most recent
period of maximum tides, and most rigorous climate, occurred about 1433, its effect
being felt, however, for several centuries before and after that year. The minimum tidal
effect prevailed about A. D. 550, and it will occur again about the year 2400.
During the latest period of benevolent climate, snow and ice were little known on the
coast of Europe and in the seas about Iceland and Greenland. Then the Vikings sailed
freely over northern seas, monks went back and forth between Ireland and ‘Thule’ or
Iceland, and there was easy intercourse between Great Britain and the Scandinavian
countries. When Eric the Red voyaged to Greenland, according to the Sagas, he came
from the sea to land at the middle glacier from thence he went south along the coast to
see if the land was habitable. The first year he wintered on Erik’s Island. .. This was
probably in the year 984. There is no mention in the Sagas that Eric was hampered by
drift ice in the several years of his exploration of the island; nor is there mention of drift
ice anywhere about Greenland, or between Greenland and Wineland. Eric’s route as
described in the Sagas - proceeding directly west from Iceland and then down the east
coast of Greenland - is one that would have been impossible during recent centuries. In
the thirteenth century the Sagas contain for the first time a warning that those who sail for
Greenland should not make the coast too directly west of Iceland on account of the ice in
the sea, but no new route is then recommended. At the end of the fourteenth century,
however, the old sailing route was abandoned and new sailing directions were given for a
more south-westerly course that would avoid the ice.
The early Sagas spoke, too, of the abundant fruit of excellent quality growing in
Greenland, and of the number of cattle that could be pastured there. The Norwegian
settlements were located in places that are now at the foot of glaciers. There are Eskimo
legends of old houses and churches buried under the ice. The Danish Archaeological
Expedition sent-out by the National Museum of Copenhagen was never able to find all of
the villages mentioned in the old records. But, its excavations indicated clearly that the
colonists lived in a climate definitely milder than the present one.
But these bland climatic conditions began to deteriorate in the thirteenth century. The
Eskimos began to make troublesome raids, perhaps because their northern sealing
grounds were frozen over and they were hungry. They attacked the western settlement
near the present Ameralik Fiord, and when an official mission went out from the eastern
colony about 1342, not a single colonist could be found only a few cattle remained. The
eastern settlement was wiped out some time after 1418 and the houses and churches
destroyed by fire. Perhaps the fate of the Greenland colonies was in part due to the fact
that ships from Iceland and Europe were finding it increasingly difficult to reach
Greenland and the colonists had to be left to their own resources.
The climatic rigours experienced in Greenland in the thirteenth and fourteenth
centuries were felt also in Europe in a series of unusual events and extraordinary catastrophes.
The seacoast of Holland was devastated by storm floods. Old Icelandic records
say that in the winters of the early 1300’s packs of wolves crossed on the ice from
Norway to Denmark. The entire Baltic froze over, forming a bridge of solid ice between
Sweden and the Danish islands. Pedestrians and carriages crossed the frozen sea and
hostelries were put up on the ice to accommodate them. The freezing of the Baltic seems
to have shifted the course of storms originating in the low pressure belt south of Iceland.
In southern Europe, as a result, there were unusual storms, crop failures, famine, and
distress. Icelandic literature abounds in tales of volcanic eruptions and other violent
natural catastrophes that occurred during the fourteenth century.
What of the previous era of cold and storms, which should have occurred about the
third or fourth century B. C., according to the tidal theory? There are shadowy hints in
early literature and folklore. The dark and brooding poetry of the Edda deals with a great
catastrophe, the Fimbul-winter or Gotterdammerung, when frost and snow ruled the
world for generations. When Pytheas journeyed to the seas north of Iceland in 330 B.C.,
he spoke of the mare pigrum, a sluggish, congealed sea. Early history contains striking
suggestions that the restless movements of the tribes of northern Europe - the southward
migrations of the ‘barbarians’ who shook the power of Rome - coincided with periods of
storms, floods, and other climatic catastrophes that forced their migrations. Large-scale
inundations of the sea destroyed the homelands of the Teutons and Cumbrians in Jutland
and sent them southward into Gaul Tradition among the Druids said that their ancestors
had been expelled from their lands on the far side of the Rhine by enemy tribes and by ‘a
great invasion of the ocean’. And about the year 700 B.C. the trade routes for amber,
found on the coasts of the North-Sea, were suddenly shifted to the east. The old route
came down along the Elbe, the Weser, and the Danube, through the Brenner Pass to Italy.
The new route followed the Vistula, suggesting that the source of supply was then the
Baltic. Perhaps storm floods had destroyed the earlier amber districts, as they invaded
these same regions eighteen centuries later.
All these ancient records of climatic variations seemed, to Pettersson an indication that
cyclic changes in the oceanic circulation and in the conditions of the Atlantic had
occurred. ‘No geologic alteration that could influence the climate has occurred for the
past six or seven centuries’, he wrote. The very nature of these phenomena - floods,
inundations, ice blockades - suggested to him a dislocation of the oceanic circulation.
Applying the discoveries in his laboratory on Gulmarfiord, he believed that the climatic
changes were brought about as the tide-induced submarine waves disturbed the deep
waters of polar seas.
Although tidal movements are often weak at the surface of these
seas, they set up strong pulsations at the submarine boundaries, where there is a layer of
comparatively fresh, cold water lying upon a layer of salty, warmer water. In the years or
the centuries of strong tidal forces, unusual quantities of warm Atlantic water press into
the Arctic Sea at deep levels, moving in under the ice. Then thousands of square miles of
ice that normally remain solidly frozen undergo partial thawing and break up. Drift ice, in
extraordinary volume, enters the Labrador Current and is carried southward into the
Atlantic. This changes the pattern of surface circulation, which is so intimately related to
the winds, the rainfall, and the air temperatures. For the drift ice then attacks the Gulf
Stream south of Newfoundland and sends it on a more - easterly course, deflecting the
streams of warm surface water that usually bring a softening effect to the climate of
Greenland, Iceland, Spitsbergen, and northern Europe. The position of the low-pressure
belt south of Iceland is also shifted, with further direct effect on European climate.
Although the really catastrophic disturbances of the polar regime come only, every
eighteen centuries, according to Pettersson, there are also rhythmically occurring periods
that fall at varying intervals - for example, every 9, 18, or 36 years. These correspond to
other tidal cycles. They produce climatic variations of shorter period and of less drastic
nature.
The year 1903 for instances was memorable for its outbursts of polar ice in the Arctic
and for the repercussions on Scandinavian fisheries. There was ‘a general failure of cod
herring, and other fish along the coast from Finmarken and Lofoten to the Skagerrak and
Kattegat. The greater part of the Barents Sea was covered with pack ice up to May, the
ice border approaching closer to the Murman and Finmarken coasts than ever before.
Herds of arctic seals visited these coasts, and some species of the arctic white fish
extended their migrations to the Christiana Fiord and even entered into the Baltic. This
outbreak of ice came in a year when earth, moon, and sun were in a relative position that
gives a secondary maximum of the tide-producing forces. The similar constellation of
1912 was another great ice year in the Labrador Current - a year that brought the disaster
of the Titanic.
Now in our own lifetime we are witnessing a startling alteration of climate, and it is
intriguing to apply Otto Pettersson’s ideas as a possible explanation. It is now established
beyond question that a definite change in the arctic climate set in about 1900, that it
became astonishingly marked about 1930, and that it is now spreading into sub-arctic and
temperate regions. The frigid top of the world is very clearly warming up.
The trend towards a milder climate in the Arctic is perhaps most strikingly apparent in
the greater ease of navigation in the North Atlantic and the Arctic Sea. In 1932, for
example, the Knipowitsch sailed ar6und Franz Josef Land for the first time in the history
of arctic voyaging. And three years later the Russian ice-breaker Sadko went from the
northern tip of Novaya Zemlya to a point north of Severnaya Zemlya (Northern Land)
and thence to 82° 41' north latitude - the northernmost point ever reached by a ship under
its own power.
In 1940 the whole northern coast of Europe and Asia was remarkably free from ice
during the summer months, and more than 100 vessels engaged in trade via the arctic
routes. In 1942 a vessel unloaded supplies at the west Greenland port of Upernivik
(latitude 72° 43' N) during Christmas week in almost complete winter darkness. During
the forties the season for shipping coal from West Spitsbergen ports lengthened to seven
months, compared with three at the beginning of the century. The season when pack ice
lies about Iceland became shorter by about two months than it was a century ago. Drift
ice in the Russian sector of the Arctic Sea decreased by a million square kilometres
between 1924 and 1944, and in the Laptev Sea two islands of fossil ice melted away
completely, then- position being marked by submarine shoals.
Activities in the nonhuman world also reflect the warming of the Arctic - the changed
habits and migrations of many fishes, birds, land mammals, and whales.
Many new birds are appearing in far northern lands for the first time in our records.
The long list of southern visitors - birds never reported in Greenland before 1920 —
includes the American velvet scoter, the greater yellowlegs, American avocet, black
browed albatross, northern cliff swallow, ovenbird, common crossbill, Baltimore oriole,
and Canada warbler. Some high-arctic forms, which thrive hi cold climates, have shown
their distaste for the warmer temperatures by visiting Greenland in sharply decreasing
numbers. Such abstainers include the northern horned lark, the grey plover, and the
pectoral sandpiper. Iceland too has had an extraordinary number of boreal and even subtropical
avian visitors since 1935, coming both from America and Europe. Wood
warblers, skylarks and Siberian ruby throats, scarlet grosbeaks, pipits, and thrushes now
provide exciting fare for Icelandic bird watchers.
When the cod first appeared at Angmagssalik in Greenland in 1912, it was a new and
strange fish to the Eskimos and Danes. Within their memory it had never before appeared
on the east coast of the island. But they began to catch it, and by the 1930$ it supported
so substantial a fishery in the area that the natives had become dependent upon it for
food. They were also using its oil as fuel for their lamps and to heat their houses.
On the west coast of Greenland, too, the cod was. a rarity at the turn of the century,
although there was a small fishery, taking about 500 tons a year, at a few places on the
southwest coast. About 1919 the cod began to move north along the west Greenland coast
and to become more abundant. The centre of the fishery has moved 300 miles farther
north, and the catch is now about 15,000 tons a year.
Other fishes seldom or never before reported in Greenland have appeared there. The
coalfish or green cod is a European fish so foreign to Greenland waters that when two of
them were caught in 1831 they were promptly preserved in salt and sent to the
Copenhagen Zoological Museum. But since 1924 this fish has often been found among
the cod shoals. The haddock, cusk, and ling, unknown in Greenland waters until about
1930, are now taken regularly. Iceland, too, has strange visitors - warmth-loving southern
fishes, like the basking shark, the grotesque sunfish, the six-gilled shark, the swordfish,
and the horse mackerel. Some of these same species have penetrated into the Barents and
White seas and along the Murman-coast.
As the chill of he northern waters has abated and the fish have moved pole ward, the
fisheries around Iceland have expanded enormously, and it has become profitable for
trawlers to push on to Bear Island, Spitsbergen, and the Barents These waters now yield
perhaps two billion pounds of cod a year —the largest catch of a single species by any
fishery in the world. But its existence is tenuous. If the cycle turns, the waters begin to
chill, and the ice floes creep southward again, there is nothing man can do that will
preserve the arctic fisheries.
But for the present, the evidence that the top of the world is growing warmer is to be
found on every hand. The recession of the northern glaciers is going on at such a rate that
many smaller ones have already disappeared. If the present rate of melting continues
others will soon follow them.
The melting away of the snowfields in the Opdal Mountains in Norway has exposed
wooden-shafted arrows of a type used about A. D. 400 to 500. This suggests that the snow
cover in this- region must now be less than it has been at any time within the past 1,400
to 1,500 years.
The glaciologist Hans Ahlmatin reports that most Norwegian glaciers are living only
on their own mass without receiving any annual fresh supply of snow; that in the Alps
there has been a general retreat and shrinkage of glaciers during the last decades, which
became ‘catastrophic’ in the summer of 1947; and that all glaciers around the Northern
Atlantic coasts are shrinking. The most rapid recession of all is occurring in Alaska,
where the Muir Glacier receded about 10.5 kilometres in 12 years.
At present the vast Antarctic glaciers are an enigma; no one can say whether they also
are melting away, or at what rate. But reports from other parts of the world show that the
northern glaciers are not the only ones that are receding. The glaciers of several East
African high volcanoes have been diminishing since they were first studied in the 1800’s
- very rapidly since 1920 - and there is glacial shrinkage in the Andes and also in, the
high mountains of central Asia.
The milder arctic and sub-arctic climate seems already to have resulted in longer
growing seasons and better crops. The cultivation of oats has improved in Iceland. In
Norway good seed years are now the rule rather than the exception, and even in northern
Scandinavia, the trees have spread rapidly above their former limber lines, and both pine
and spruce are making a quicker annual growth than they have for some time.
The countries where the most striking changes are taking place are those whose
climate is most directly under the control of the North Atlantic currents. Greenland,
Iceland, Spitsbergen, and all of northern Europe, as we have seen, experience heat and
cold, drought and flood in accordance with the varying strength and warmth of the
eastward- and northward-moving currents of the Atlantic. Oceanographers who have
been studying the matter during the 19403 have discovered many significant changes in
the temperature and distribution of great masses of ocean water. Apparently the branch of
the Gulf Stream that flows past Spitsbergen has so increased in volume that it now brings
in a great body of warm water. Surface waters of the North Atlantic show rising
temperatures; so do the deeper layers around Iceland and Spitsbergen. Sea temperatures
in the North Sea and along the coast of Norway have been growing warmer since the
1920’s.
Unquestionably, there are other agents at work in bringing about the climatic changes
in the Arctic and sub-Arctic regions. For one thing, it is almost certainly true that we are
still in the warming-up stage following the last Pleistocene glaciations - that the world’s
climate, over the next thousands of years, will grow considerably warmer before
beginning a downward swing into another Ice Age. But what we are experiencing now is
perhaps a climatic change of shorter duration, measurable only in decades or centuries.
Some scientists say that there must have been a small increase in solar activity, changing
the pattern of air circulation and causing the southerly winds to blow more frequently in
Scandinavia and Spitsbergen; changes in ocean currents, according to this view, are
secondary effects of the shift of prevailing winds.
But if, as Professor Brooks thinks, the Pettersson tidal theory has as good a foundation
as that of changing solar radiation, then it is interesting to calculate where our twentieth century
situation fits into the cosmic scheme of the shifting cycles of the tides. The great
tides at the close of the Middle Ages, with their accompanying snow and ice, furious
winds, and inundating floods, are more than five centuries behind us. The era of weakest
tidal movements, with a climate as benign as that of the early Middle Ages, is about four
centuries ahead. We have therefore begun to move strongly into a period of warmer,
milder weather. There will be fluctuations, as earth and sun and moon move through
space and the tidal power waxes and wanes. But the long trend is toward a warmer earth;
the pendulum is swinging."
from Rachel Carson, The Sea Around Us (1951)
'CLIMATIC VARIATIONS IN HISTORIC AND PREHISTORIC TIME'
By Prof. Otto PETTERSON
SEE ALSO
'CLIMATE CHANGE AND ITS COSMIC ORIGINS' Richard K. Moore
"The emerging electric model of the universe holds the key to understanding the causes of long and short-term climate variation. The pattern of variation has very specific characteristics, characteristics that match the behavior of a noisy electrical circuit. The electric model reveals that the Earth is indeed connected to a cosmic electrical circuit, a circuit that is subject to the kind of noise that could produce the patterns seen in the Earth’s temperature record."
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